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Sept. 18, 2008 -- Whether you've got Barack Obama posters in your yard or John McCain stickers on the back of your car, your strong beliefs may be linked to your physiology.

A new study, published in Science, shows that Americans with strong political opinions whose bodies react more strongly to threatening pictures and sudden loud noises tended to support causes like defense spending and capital punishment.

The reason, the researchers suggest, is that these participants' views may be linked to a concern with protecting their group -- in this case the U.S. -- from perceived threats.

Those people with lesser physical reactions to threatening pictures and sounds were more likely to support causes such as gun control and foreign aid.

Douglas Oxley, from the department of political science at University of Nebraska-Lincoln, and a team of researchers studied 46 people with strong political beliefs. These participants, chosen for having strong political views, were identified through random phone calls in spring 2007. Participants filled out a questionnaire about their political beliefs, personality traits, and demographic characteristics.

Later, they were hooked up to machines to measure their physiological reactions to threatening stimuli, such as a picture of a large spider on the face of a frightened person, vs. nonthreatening stimuli, such as a picture of a rabbit.

The amount of reaction was measured by a machine that tests the conductivity of the skin. This is important because arousal can increase moisture on the outer layers of the skin, which then increases skin conductivity.

In another test, participants' blinks were measured after they heard an unexpected loud noise. Harder blinks are linked to higher level of fear, according to researchers.

The researchers emphasize that their findings can't confirm cause and effect.

So next time you are trying to convert a strong-minded friend to your way of political thinking, don't be disappointed if your best arguments are unsuccessful.

The authors conclude, "Our findings suggest that political attitudes vary with physiological traits linked to divergent manners of experiencing and processing environmental threats. Consequently, our research provides one possible explanation for both the lack of malleability in the beliefs of individuals with strong political convictions and for the associated ubiquity of political conflict."